1. Field of the Invention
The present invention generally relates to a video device, and more particularly, to a state detection technique for a video device.
2. Description of Related Art
It is well known in the video device industry that the phase of a video signal has to be locked before the video signal is processed in order to process the video signal correctly.
A video signal further carries a color burst signal for denoting the phase of color information carried by the video signal. A chroma detector is used for detecting the color burst signal so that the phase of the color information can be locked and the correct color information can be decoded subsequently.
However, usually only one chroma detector is disposed in a video device. The chroma detector is used for processing an input signal and accordingly generating an output signal, and the chroma detector is also used for detecting whether the phase of the input signal can be locked. The chroma detector may not be able to lock the phase of the input signal when the signal source is changed, for example, when the input signal is changed from the National Television System Committee (NTSC) format to the Phase Alternating Line (PAL) format.
Accordingly, when the chroma detector cannot lock the phase of the input signal, a controller of the video device switches the operation state of the chroma detector according to a finite state machine (FSM) until the chroma detector can lock the phase of the input signal.
Generally, it takes a very long time for the controller to switch the operation state of the chroma detector according to the FSM. Besides, if the chroma detector cannot process the input signal normally and accordingly, a transient problem may be caused in a displayed image because the controller needs to continuously switch the operation state of the chroma detector.
Moreover, it is not necessary to change the operation state of the chroma detector when the strength of the input signal is reduced. However, in the conventional technique, the controller may mistakenly determine that the chroma detector cannot lock the phase of the input signal normally and accordingly switch the operation state of the chroma detector to re-lock the phase of the input signal. As a result, the quality of a displayed image may be affected.